Gold Stained Glass Windows Purify the Air

Scientists have discovered that, in medieval churches, stained glass windows painted with gold purify the air when heated by the sun. The researchers hope that this discovery could also be used for modern technologies, since the chemical reaction involved is very energy-efficient.

Associate Professor Zhu Huai Yong, from Queensland University of Technology's School of Physical and Chemical Sciences, said that church windows stained with gold paint purify the air when they are lit up by sunlight. Credit: QUT: Erika FishThe scientists, from Queensland University of Technology, explained that the gold paint in the windows consists of gold nanoparticles of different sizes. When energized by the sun, the electrons in the gold nanoparticles become very active. When the electromagnetic field of the sunlight couples with the electrons' oscillations, it creates a resonance.

As the scientists explain, this reaction can increase the nanoparticles' magnetic field strength by up to 100 times, enough to break apart pollutant molecules in the air. Some of these airborne pollutants include methanol, carbon monoxide, and volatile organic chemicals (VOCs), which give new carpet, paint, and furniture that distinctive "new" smell.

The byproduct of the chemical reaction with the gold nanoparticles is small quantities of carbon dioxide, which the researchers say is much safer compared to the pollutants.

"For centuries people appreciated only the beautiful works of art, and long life of the colors, but little did they realize that these works of art are also, in modern language, photocatalytic air purifiers with nanostructured gold catalysts," Professor Zhu Huai Yong of Queensland said.

Zhu hopes that future technology might take advantage of the benefits of using gold nanoparticles to drive chemical reactions, since it's much more efficient than conventional chemical reactions. In normal chemical reactions, the entire material heats up, but with the "solar-powered" gold nanoparticles, only the gold heats up.

"Once this technology can be applied to produce specialty chemicals at ambient temperature, it heralds significant changes in the economy and environmental impact of the chemical production," he said.